The subject matter disclosed herein relates to a steam turbine nozzle assembly, or diaphragm stage. Specifically, the subject matter disclosed herein relates to an alignment system for a steam turbine nozzle assembly.
Steam turbines include static nozzle assemblies that direct flow of a working fluid into turbine buckets connected to a rotatable rotor. The nozzle construction (including a plurality of nozzles, or “airfoils”) is sometimes referred to as a “diaphragm” or “nozzle assembly stage.” Steam turbine diaphragms include two halves, which are assembled around the rotor, creating horizontal joints between these two halves. Each turbine diaphragm stage is vertically supported by support bars, support lugs or support screws on each side of the diaphragm at the respective horizontal joints. The horizontal joints of the diaphragm also correspond to horizontal joints of the turbine casing, which surrounds the steam turbine diaphragm.
Conventionally, the nozzle assembly stages are aligned either with the rotor in place, or without the rotor, using a hard wire or laser measurement. In one conventional approach, the lower half of the nozzle assembly stage (or, nozzle lower half) and the rotor are aligned without the upper half of the nozzle assembly stage (or, nozzle upper half) and/or the upper half of the turbine casing in place. In this approach, measurements are made between the lower half and the rotor at the bottom and each respective side of the turbine. In a second conventional approach, the nozzle upper half and casing upper half (as well as the respective lower halves) are in place without the rotor. In this approach, measurements are made between the bearing centerline locations and the nozzle assembly centerline.
In either case, conventional approaches to alignment/adjustment of steam path components requires separately measuring the relative position of components, disassembling portions of the components, and adjusting shims used to fine-tune the position of these components. Subsequent to the adjustment of the shims, the components are reassembled, and measurement is conducted yet again. This process may be iterated a number of times until the measurements fall within a predetermined acceptable range. The iterative nature of this process can be both time consuming and costly.